Hydroformylation of olefins in the presence of Group VIII transition metal carbonyl complex catalysts to produce aldehydes is well known. Rhodium complexes such as HRh(CO)(PPh.sub.3).sub.3 are favored because they are active under mild conditions and are highly selective toward linear aldehyde products. Since rhodium is expensive, catalyst lifetime is important for commercial hydroformylation processes that use such rhodium catalysts. Matsumoto et al. (U.S. Pat. No. 4,215,077) teach to prolong the lifetime of rhodium catalysts by including a diphosphinoalkane in the process. Catalyst lifetime improves; however, the ratio of linear to branched aldehyde products is limited when a diphosphinoalkane is used. For example, the linear/branched ratio of aldehydes is typically about 7:1 at best when the catalysts of U.S. Pat. No. 4,215,077 are used to hydroformylate allyl alcohol. Higher selectivity to the linear aldehydes is desirable because the linear end-products are often more valuable than those derived from branched aldehydes.
Hydroformylation catalysts containing more than one Group VIII metal compound are known. Chang (U.S. Pat. No. 4,453,019) teaches the use of mixed metal catalysts in the hydroformylation of olefins to produce linear aldehydes and alcohols. The catalyst system includes a first transition metal compound, which may be a neutral Group VIII metal complex such as HRh(CO)(PPh.sub.3).sub.3, and an anionic transition metal compound of the formula M.sup.+n [H.sub.y A.sub.x L.sub.x ].sup.-n wherein A can be a Group VIII(a) metal (iron, ruthenium, osmium). The latter anionic complexes are prepared by deprotonation of metal hydride compounds or reduction of neutral metal carbonyls. The preferred olefins are unfunctionalized olefins, since hydroxyl groups and halogens are known to deactivate the catalysts (column 3, lines 30-35).
Cooper (U.S. Pat. No. 4,388,477) teaches a hydroformylation process that employs an unmodified rhodium-cobalt catalyst. This bimetallic catalyst gives a relatively high proportion of branched aldehydes with unfunctionalized olefins such as propylene.
Pettit (U.S. Pat. No. 4,306,084) teaches to use a ruthenium carbonyl catalyst under basic conditions (pH 8-11) in aqueous media to selectively give linear aldehyde and alcohol products from the hydroformylation of unfunctionalized olefins such as propylene and 1-butene. Similarly, Laine (U.S. Pat. No. 4,226,845) teaches to use two or more Group VIII metal carbonyl compounds, one of which is ruthenium, in the presence of a base to hydroformylate unfunctionalized olefins.
Hignett et al. (U.S. Pat. No. 4,200,592) teach a homogeneous catalyst system for isomerization and hydroformylation of internal olefins to give linear aldehydes. The catalyst system includes a Rh(I) complex and a complex of a transition metal other than rhodium from Group VI or Group VIII. Only unfunctionalized olefins are used, and the linear/branched aldehyde product ratios reported are typically less than 2:1.
Slaugh (U.S. Pat. No. 3,239,566) teaches to hydroformylate olefins with rhodium or ruthenium-containing catalysts. Bimetallic catalyst systems are not taught, and the examples are specific to unfunctionalized olefins.
Still lacking in the art is a hydroformylation process that gives high selectivity to linear aldehydes, particularly when allyl alcohol is used. Catalysts that have a reduced tendency to deactivate during hydroformylation--yet still give good selectivity to linear aldehydes--are needed.